I have mainly covered race and gender. I am not aware of current datasets on disability or the chances of gay candidates, and would welcome any information.

The overall story is of under-recognised progress on ethnic representation when it comes to the gateway of Parliamentary selections, but less progress than many people think on gender. And there are later issues about the value given to seniority in British politics, which means that getting a more balanced intake may be reflected in who holds power more slowly.

The current rate of progress is about three times as fast as is being claimed. The methodology of a linear projection of this sort is flawed, but those using it should more accurately say 25-30 years.

Isn't that also too long?

Maybe. But it also depends what the goal is. For me, the primary objectives is "fair chances and no unfair barriers" to all candidates, whatever their background. That is achieved if women win 50% of selections and BME candidates 8% of selections, with the number fluctuating higher and lower, according to random variations. The "Parliament that looks like Britain" is a by=product of this, and takes three to five Parliaments to come through fully. Those who wish to accelerate progress further have to make a trade-off with fair chances: for example, giving absolute priority to a gender balanced Commons overall could most directly be achieved by asking parties to select no men at all for two Parliaments, but would obviously have an impact on fair chances by producing 100% female intakes to try to rebalance the current 5-1 split in the House.

How are the parties doing?

It is estimated that around 7% of the class of 2010 will be made up of non-white candidates. This would be unprecedented, and close to the 8% benchmark, but it is made up of different outcomes across different parties.

Labour has made unprecedented recent progress. 2% of Labour MPs before 1997 were non-white, and so were just 2% of its landslide intake. But 7.5% of its class of 2005 were BME, and 10% of new candidates. Labour is the first party in western Europe to show that an 'ethnic penalty' to fair chances can be defeated.

The Conservatives have done very well in this Parliament. They elected 38 white men and one woman in their class of 2001, and have only two non-white MPs (1%). But they are now selecting BME candidates in 5% of new selections. That is not yet the 8% mark they might aspire to - but it means the Conservative party in 2009 is now where Labour was in 2001. The challenge is to ensure this is not a "one-off" event as part of the Cameroon rebranding.

The LibDems are stuck, with no candidates in winnable seats. They often have a high number of BME candidates - more than the Conservatives - but they are very much selected in areas with high minority ethnic populations, and the LibDems have a weak chance of winning these seats. They need to break this "ethnic candidates for ethnic seats" model if they wish to have non-white MPs in the LibDem parliamentary party. (Considering all black shortlists is not going to help with this problem, unless they will hold them in St Ives, Winchester or York: what they need to do is hold a national all member competition to identify perhaps five talented individuals, so that they have a high profile in future Westminster, European and other selections).

The number of black, Asian and mixed race candidates at the next election is unlikely to be affected by political swing.

A couple of MPs have suggested to me that I must be relying on projections about the electoral outcome. Parmjit Dhanda made this point in the Commons evidence session. Interestingly, (and counter-intuitively) this is not the case: the number is unlikely to be affected at all by the relative national performance of the Labour and Conservative parties, for two reasons.

Firstly, those BME Labour MPs with relatively high BME populations tend to have fairly safe seats, and that is true of a fair share of the seats held by black and Asian MPs.

Secondly, among marginal and contested seats, there looks set to be a more or less one for one off-setting number of gains and losses between Labour and the Conservatives, whichever party does well.

The exception to this is that the net number is likely to be one more or one less depending on whether Dawn Butler or Sarah Teather wins in Brent, where Butler begins as the favourite. (If the LibDems do well against Labour generally, they have no BME candidates in these target seats, so the defeat of a Labour BME MP does not then see a LibDem elected elsewhere).